Add "std" feature flag (#476)

* core feature

Signed-off-by: Yoshua Wuyts <yoshuawuyts@gmail.com>

* introduce std + default features

Signed-off-by: Yoshua Wuyts <yoshuawuyts@gmail.com>

* test std features on ci

Signed-off-by: Yoshua Wuyts <yoshuawuyts@gmail.com>

* finish up all features

Signed-off-by: Yoshua Wuyts <yoshuawuyts@gmail.com>

* Fix task_local macro

* Remove crossbeam-channel and futures-timer from std

* Move future::timeout() behind cfg_default

.github/workflows/ci.yml

@@ -40,6 +40,12 @@ jobs:
         command:  check
         args: --features unstable --all --benches --bins --examples --tests
 
+    - name: check std only
+      uses: actions-rs/cargo@v1
+      with:
+        command:  check
+        args: --no-default-features --features std
+
     - name: tests
       uses: actions-rs/cargo@v1
       with:

Cargo.toml

@@ -21,32 +21,54 @@ features = ["docs"]
 rustdoc-args = ["--cfg", "feature=\"docs\""]
 
 [features]
-default = []
-docs = ["unstable", "attributes"]
-unstable = ["broadcaster"]
-attributes = ["async-attributes"]
+default = [
+  "std",
+  "async-task",
+  "crossbeam-channel",
+  "crossbeam-deque",
+  "futures-timer",
+  "kv-log-macro",
+  "log",
+  "mio",
+  "mio-uds",
+  "num_cpus",
+  "pin-project-lite",
+]
+docs = ["unstable"]
+unstable = ["default", "broadcaster"]
+std = [
+  "async-macros",
+  "crossbeam-utils",
+  "futures-core",
+  "futures-io",
+  "memchr",
+  "once_cell",
+  "pin-project-lite",
+  "pin-utils",
+  "slab",
+]
 
 [dependencies]
 async-attributes = { version = "1.1.0", optional = true }
-async-macros = "1.0.0"
-async-task = "1.0.0"
+async-macros = { version = "1.0.0", optional = true }
+async-task = { version = "1.0.0", optional = true }
 broadcaster = { version = "0.2.6", optional = true, default-features = false, features = ["default-channels"] }
-crossbeam-channel = "0.3.9"
-crossbeam-deque = "0.7.1"
-crossbeam-utils = "0.6.6"
-futures-core = "0.3.0"
-futures-io = "0.3.0"
-futures-timer = "1.0.2"
-kv-log-macro = "1.0.4"
-log = { version = "0.4.8", features = ["kv_unstable"] }
-memchr = "2.2.1"
-mio = "0.6.19"
-mio-uds = "0.6.7"
-num_cpus = "1.10.1"
-once_cell = "1.2.0"
-pin-project-lite = "0.1"
-pin-utils = "0.1.0-alpha.4"
-slab = "0.4.2"
+crossbeam-channel = { version = "0.3.9", optional = true }
+crossbeam-deque = { version = "0.7.1", optional = true }
+crossbeam-utils = { version = "0.6.6", optional = true }
+futures-core = { version = "0.3.0", optional = true }
+futures-io = { version = "0.3.0", optional = true }
+futures-timer = { version = "1.0.2", optional = true }
+kv-log-macro = { version = "1.0.4", optional = true }
+log = { version = "0.4.8", features = ["kv_unstable"], optional = true }
+memchr = { version = "2.2.1", optional = true }
+mio = { version = "0.6.19", optional = true }
+mio-uds = { version = "0.6.7", optional = true }
+num_cpus = { version = "1.10.1", optional = true }
+once_cell = { version = "1.2.0", optional = true }
+pin-project-lite = { version = "0.1", optional = true }
+pin-utils = { version = "0.1.0-alpha.4", optional = true }
+slab = { version = "0.4.2", optional = true }
 
 [dev-dependencies]
 femme = "1.2.0"

src/future/future/mod.rs

@@ -144,8 +144,8 @@ extension_trait! {
         /// dbg!(a.await);
         /// # })
         /// ```
+        #[cfg(all(feature = "default", feature = "unstable"))]
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
-        #[cfg(any(feature = "unstable", feature = "docs"))]
         fn delay(self, dur: Duration) -> impl Future<Output = Self::Output> [DelayFuture<Self>]
         where
             Self: Future + Sized
@@ -167,8 +167,8 @@ extension_trait! {
         /// assert_eq!(future.await, 1);
         /// # })
         /// ```
+        #[cfg(feature = "unstable")]
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
-        #[cfg(any(feature = "unstable", feature = "docs"))]
         fn flatten(self) -> impl Future<Output = <<Self as Future>::Output as IntoFuture>::Output> [FlattenFuture<Self, <<Self as Future>::Output as IntoFuture>::Future>]
         where
             Self: Future + Sized,
@@ -206,7 +206,7 @@ extension_trait! {
             # });
             ```
         "#]
-        #[cfg(any(feature = "unstable", feature = "docs"))]
+        #[cfg(feature = "unstable")]
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
         fn race<F>(
             self,
@@ -252,7 +252,7 @@ extension_trait! {
             # Ok(()) }) }
             ```
         "#]
-        #[cfg(any(feature = "unstable", feature = "docs"))]
+        #[cfg(feature = "unstable")]
         #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
         fn try_race<F: std::future::Future, T, E>(
             self,

src/future/mod.rs

@@ -53,13 +53,16 @@ pub use future::Future;
 pub use pending::pending;
 pub use poll_fn::poll_fn;
 pub use ready::ready;
-pub use timeout::{timeout, TimeoutError};
 
 pub(crate) mod future;
 mod pending;
 mod poll_fn;
 mod ready;
-mod timeout;
+
+cfg_default! {
+    pub use timeout::{timeout, TimeoutError};
+    mod timeout;
+}
 
 cfg_unstable! {
     pub use into_future::IntoFuture;

src/io/mod.rs

@@ -269,48 +269,54 @@
 //! [`Result`]: https://doc.rust-lang.org/std/result/enum.Result.html
 //! [`.unwrap()`]: https://doc.rust-lang.org/std/result/enum.Result.html#method.unwrap
 
-#[doc(inline)]
-pub use std::io::{Error, ErrorKind, IoSlice, IoSliceMut, Result, SeekFrom};
+cfg_std! {
+    #[doc(inline)]
+    pub use std::io::{Error, ErrorKind, IoSlice, IoSliceMut, Result, SeekFrom};
 
-pub use buf_read::{BufRead, Lines};
-pub use buf_reader::BufReader;
-pub use buf_writer::BufWriter;
-pub use copy::copy;
-pub use cursor::Cursor;
-pub use empty::{empty, Empty};
-pub use read::Read;
-pub use repeat::{repeat, Repeat};
-pub use seek::Seek;
-pub use sink::{sink, Sink};
-pub use stderr::{stderr, Stderr};
-pub use stdin::{stdin, Stdin};
-pub use stdout::{stdout, Stdout};
-pub use timeout::timeout;
-pub use write::Write;
+    pub use buf_read::{BufRead, Lines};
+    pub use buf_reader::BufReader;
+    pub use buf_writer::BufWriter;
+    pub use copy::copy;
+    pub use cursor::Cursor;
+    pub use empty::{empty, Empty};
+    pub use read::Read;
+    pub use repeat::{repeat, Repeat};
+    pub use seek::Seek;
+    pub use sink::{sink, Sink};
+    pub use write::Write;
 
-// For use in the print macros.
-#[doc(hidden)]
-pub use stdio::{_eprint, _print};
+    pub mod prelude;
 
-pub mod prelude;
+    pub(crate) mod buf_read;
+    pub(crate) mod read;
+    pub(crate) mod seek;
+    pub(crate) mod write;
 
-pub(crate) mod buf_read;
-pub(crate) mod read;
-pub(crate) mod seek;
-pub(crate) mod write;
+    mod buf_reader;
+    mod buf_writer;
+    mod copy;
+    mod cursor;
+    mod empty;
+    mod repeat;
+    mod sink;
+}
+
+cfg_default! {
+    // For use in the print macros.
+    #[doc(hidden)]
+    pub use stdio::{_eprint, _print};
 
-mod buf_reader;
-mod buf_writer;
-mod copy;
-mod cursor;
-mod empty;
-mod repeat;
-mod sink;
-mod stderr;
-mod stdin;
-mod stdio;
-mod stdout;
-mod timeout;
+    pub use stderr::{stderr, Stderr};
+    pub use stdin::{stdin, Stdin};
+    pub use stdout::{stdout, Stdout};
+    pub use timeout::timeout;
+
+    mod timeout;
+    mod stderr;
+    mod stdin;
+    mod stdio;
+    mod stdout;
+}
 
 cfg_unstable! {
     pub use stderr::StderrLock;

src/lib.rs

@@ -1,7 +1,7 @@
 //! # Async version of the Rust standard library
 //!
 //! `async-std` is a foundation of portable Rust software, a set of minimal and battle-tested
-//! shared abstractions for the [broader Rust ecosystem][crates.io]. It offers core types, like
+//! shared abstractions for the [broader Rust ecosystem][crates.io]. It offers std types, like
 //! [`Future`] and [`Stream`], library-defined [operations on language primitives](#primitives),
 //! [standard macros](#macros), [I/O] and [multithreading], among [many other things][other].
 //!
@@ -170,8 +170,17 @@
 //! version = "0.99"
 //! features = ["attributes"]
 //! ```
+//!
+//! Additionally it's possible to only use the core traits and combinators by
+//! only enabling the `std` Cargo feature:
+//!
+//! ```toml
+//! [dependencies.async-std]
+//! version = "0.99"
+//! default-features = false
+//! features = ["std"]
+//! ```
 
-#![cfg(feature = "default")]
 #![cfg_attr(feature = "docs", feature(doc_cfg))]
 #![warn(missing_docs, missing_debug_implementations, rust_2018_idioms)]
 #![allow(clippy::mutex_atomic, clippy::module_inception)]
@@ -188,16 +197,24 @@ mod utils;
 #[doc(inline)]
 pub use async_attributes::{main, test};
 
-pub mod fs;
-pub mod future;
-pub mod io;
-pub mod net;
-pub mod os;
-pub mod path;
-pub mod prelude;
-pub mod stream;
-pub mod sync;
-pub mod task;
+#[cfg(feature = "std")]
+mod macros;
+
+cfg_std! {
+    pub mod future;
+    pub mod io;
+    pub mod os;
+    pub mod prelude;
+    pub mod stream;
+    pub mod sync;
+    pub mod task;
+}
+
+cfg_default! {
+    pub mod fs;
+    pub mod path;
+    pub mod net;
+}
 
 cfg_unstable! {
     pub mod pin;
@@ -213,5 +230,3 @@ cfg_unstable! {
     #[doc(inline)]
     pub use std::{write, writeln};
 }
-
-mod macros;

src/macros.rs

@@ -165,3 +165,55 @@ macro_rules! eprintln {
         }
     );
 }
+
+/// Declares task-local values.
+///
+/// The macro wraps any number of static declarations and makes them task-local. Attributes and
+/// visibility modifiers are allowed.
+///
+/// Each declared value is of the accessor type [`LocalKey`].
+///
+/// [`LocalKey`]: task/struct.LocalKey.html
+///
+/// # Examples
+///
+/// ```
+/// #
+/// use std::cell::Cell;
+///
+/// use async_std::task;
+/// use async_std::prelude::*;
+///
+/// task_local! {
+///     static VAL: Cell<u32> = Cell::new(5);
+/// }
+///
+/// task::block_on(async {
+///     let v = VAL.with(|c| c.get());
+///     assert_eq!(v, 5);
+/// });
+/// ```
+#[cfg(feature = "default")]
+#[macro_export]
+macro_rules! task_local {
+    () => ();
+
+    ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = $init:expr) => (
+        $(#[$attr])* $vis static $name: $crate::task::LocalKey<$t> = {
+            #[inline]
+            fn __init() -> $t {
+                $init
+            }
+
+            $crate::task::LocalKey {
+                __init,
+                __key: ::std::sync::atomic::AtomicU32::new(0),
+            }
+        };
+    );
+
+    ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = $init:expr; $($rest:tt)*) => (
+        $crate::task_local!($(#[$attr])* $vis static $name: $t = $init);
+        $crate::task_local!($($rest)*);
+    );
+}

src/os/unix/mod.rs

@@ -1,5 +1,10 @@
 //! Platform-specific extensions for Unix platforms.
 
-pub mod fs;
-pub mod io;
-pub mod net;
+cfg_std! {
+    pub mod io;
+}
+
+cfg_default! {
+    pub mod fs;
+    pub mod net;
+}

src/os/windows/mod.rs

@@ -1,3 +1,5 @@
 //! Platform-specific extensions for Windows.
 
-pub mod io;
+cfg_std! {
+    pub mod io;
+}

src/prelude.rs

@@ -11,35 +11,39 @@
 //! use async_std::prelude::*;
 //! ```
 
-#[doc(no_inline)]
-pub use crate::future::Future;
-#[doc(no_inline)]
-pub use crate::stream::Stream;
-#[doc(no_inline)]
-pub use crate::task_local;
+cfg_std! {
+    #[doc(no_inline)]
+    pub use crate::future::Future;
+    #[doc(no_inline)]
+    pub use crate::stream::Stream;
 
-#[doc(inline)]
-pub use crate::future::future::FutureExt;
-#[doc(inline)]
-pub use crate::stream::stream::StreamExt;
+    #[doc(inline)]
+    pub use crate::future::future::FutureExt;
+    #[doc(inline)]
+    pub use crate::stream::stream::StreamExt;
+    #[doc(no_inline)]
+    pub use crate::io::BufRead as _;
+    #[doc(no_inline)]
+    pub use crate::io::Read as _;
+    #[doc(no_inline)]
+    pub use crate::io::Seek as _;
+    #[doc(no_inline)]
+    pub use crate::io::Write as _;
 
-#[doc(no_inline)]
-pub use crate::io::BufRead as _;
-#[doc(no_inline)]
-pub use crate::io::Read as _;
-#[doc(no_inline)]
-pub use crate::io::Seek as _;
-#[doc(no_inline)]
-pub use crate::io::Write as _;
+    #[doc(no_inline)]
+    pub use crate::io::prelude::BufReadExt as _;
+    #[doc(no_inline)]
+    pub use crate::io::prelude::ReadExt as _;
+    #[doc(no_inline)]
+    pub use crate::io::prelude::SeekExt as _;
+    #[doc(no_inline)]
+    pub use crate::io::prelude::WriteExt as _;
+}
 
-#[doc(no_inline)]
-pub use crate::io::prelude::BufReadExt as _;
-#[doc(no_inline)]
-pub use crate::io::prelude::ReadExt as _;
-#[doc(no_inline)]
-pub use crate::io::prelude::SeekExt as _;
-#[doc(no_inline)]
-pub use crate::io::prelude::WriteExt as _;
+cfg_default! {
+    #[doc(no_inline)]
+    pub use crate::task_local;
+}
 
 cfg_unstable! {
     #[doc(no_inline)]

src/sync/waker_set.rs

@@ -7,12 +7,11 @@
 use std::cell::UnsafeCell;
 use std::ops::{Deref, DerefMut};
 use std::sync::atomic::{AtomicUsize, Ordering};
+use std::task::{Context, Waker};
 
 use crossbeam_utils::Backoff;
 use slab::Slab;
 
-use crate::task::{Context, Waker};
-
 /// Set when the entry list is locked.
 #[allow(clippy::identity_op)]
 const LOCKED: usize = 1 << 0;

src/task/mod.rs

@@ -118,41 +118,45 @@
 //! [`task_local!`]: ../macro.task_local.html
 //! [`with`]: struct.LocalKey.html#method.with
 
-#[doc(inline)]
-pub use std::task::{Context, Poll, Waker};
+cfg_std! {
+    #[doc(inline)]
+    pub use std::task::{Context, Poll, Waker};
 
-#[doc(inline)]
-pub use async_macros::ready;
+    #[doc(inline)]
+    pub use async_macros::ready;
+}
 
-pub use block_on::block_on;
-pub use builder::Builder;
-pub use current::current;
-pub use join_handle::JoinHandle;
-pub use sleep::sleep;
-pub use spawn::spawn;
-pub use task::Task;
-pub use task_id::TaskId;
-pub use task_local::{AccessError, LocalKey};
+cfg_default! {
+    pub use block_on::block_on;
+    pub use builder::Builder;
+    pub use current::current;
+    pub use task::Task;
+    pub use task_id::TaskId;
+    pub use join_handle::JoinHandle;
+    pub use sleep::sleep;
+    pub use spawn::spawn;
+    pub use task_local::{AccessError, LocalKey};
 
-#[cfg(any(feature = "unstable", test))]
-pub use spawn_blocking::spawn_blocking;
-#[cfg(not(any(feature = "unstable", test)))]
-pub(crate) use spawn_blocking::spawn_blocking;
+    use builder::Runnable;
+    use task_local::LocalsMap;
 
-use builder::Runnable;
-use task_local::LocalsMap;
+    mod block_on;
+    mod builder;
+    mod current;
+    mod executor;
+    mod join_handle;
+    mod sleep;
+    mod spawn;
+    mod spawn_blocking;
+    mod task;
+    mod task_id;
+    mod task_local;
 
-mod block_on;
-mod builder;
-mod current;
-mod executor;
-mod join_handle;
-mod sleep;
-mod spawn;
-mod spawn_blocking;
-mod task;
-mod task_id;
-mod task_local;
+    #[cfg(any(feature = "unstable", test))]
+    pub use spawn_blocking::spawn_blocking;
+    #[cfg(not(any(feature = "unstable", test)))]
+    pub(crate) use spawn_blocking::spawn_blocking;
+}
 
 cfg_unstable! {
     pub use yield_now::yield_now;

src/task/task_local.rs

@@ -5,57 +5,6 @@ use std::sync::atomic::{AtomicU32, Ordering};
 
 use crate::task::Task;
 
-/// Declares task-local values.
-///
-/// The macro wraps any number of static declarations and makes them task-local. Attributes and
-/// visibility modifiers are allowed.
-///
-/// Each declared value is of the accessor type [`LocalKey`].
-///
-/// [`LocalKey`]: task/struct.LocalKey.html
-///
-/// # Examples
-///
-/// ```
-/// #
-/// use std::cell::Cell;
-///
-/// use async_std::task;
-/// use async_std::prelude::*;
-///
-/// task_local! {
-///     static VAL: Cell<u32> = Cell::new(5);
-/// }
-///
-/// task::block_on(async {
-///     let v = VAL.with(|c| c.get());
-///     assert_eq!(v, 5);
-/// });
-/// ```
-#[macro_export]
-macro_rules! task_local {
-    () => ();
-
-    ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = $init:expr) => (
-        $(#[$attr])* $vis static $name: $crate::task::LocalKey<$t> = {
-            #[inline]
-            fn __init() -> $t {
-                $init
-            }
-
-            $crate::task::LocalKey {
-                __init,
-                __key: ::std::sync::atomic::AtomicU32::new(0),
-            }
-        };
-    );
-
-    ($(#[$attr:meta])* $vis:vis static $name:ident: $t:ty = $init:expr; $($rest:tt)*) => (
-        $crate::task_local!($(#[$attr])* $vis static $name: $t = $init);
-        $crate::task_local!($($rest)*);
-    );
-}
-
 /// The key for accessing a task-local value.
 ///
 /// Every task-local value is lazily initialized on first access and destroyed when the task

src/utils.rs

@@ -1,8 +1,7 @@
-use std::mem;
-
 /// Calls a function and aborts if it panics.
 ///
 /// This is useful in unsafe code where we can't recover from panics.
+#[cfg(feature = "default")]
 #[inline]
 pub fn abort_on_panic<T>(f: impl FnOnce() -> T) -> T {
     struct Bomb;
@@ -15,11 +14,12 @@ pub fn abort_on_panic<T>(f: impl FnOnce() -> T) -> T {
 
     let bomb = Bomb;
     let t = f();
-    mem::forget(bomb);
+    std::mem::forget(bomb);
     t
 }
 
 /// Generates a random number in `0..n`.
+#[cfg(feature = "default")]
 pub fn random(n: u32) -> u32 {
     use std::cell::Cell;
     use std::num::Wrapping;
@@ -53,6 +53,7 @@ pub fn random(n: u32) -> u32 {
 }
 
 /// Defers evaluation of a block of code until the end of the scope.
+#[cfg(feature = "default")]
 #[doc(hidden)]
 macro_rules! defer {
     ($($body:tt)*) => {
@@ -130,6 +131,30 @@ macro_rules! cfg_not_docs {
     }
 }
 
+/// Declares std items.
+#[allow(unused_macros)]
+#[doc(hidden)]
+macro_rules! cfg_std {
+    ($($item:item)*) => {
+        $(
+            #[cfg(feature = "std")]
+            $item
+        )*
+    }
+}
+
+/// Declares default items.
+#[allow(unused_macros)]
+#[doc(hidden)]
+macro_rules! cfg_default {
+    ($($item:item)*) => {
+        $(
+            #[cfg(feature = "default")]
+            $item
+        )*
+    }
+}
+
 /// Defines an extension trait for a base trait.
 ///
 /// In generated docs, the base trait will contain methods from the extension trait. In actual